Dual MAF setup.

14908 Views 56 Replies 33 Participants Last post by tdz16, Apr 19, 2006

NEAWD

Discussion Starter · Nov 12, 2005

Any thoughts? I was contemplating a dual maf setup on my DSM, which will give me twice the airflow and allow the stock ecu to control 900cc injectors with only mild tuning with an afc. I would allow one maf to be read by the ecu and have the other maf as a dummy. Now the ecu would have 1/2 the resolution as normal, but being as though the stock ecu map is rather extensive, it will only affect tunning a little. I think it would be a serious option for a fast stock ecu car. It would also allow the car to maintain the driveabillity the stock ecu offers while making a lot of power. Just some thoughts.

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roughneck9725

· #2 · Nov 12, 2005

wouldnt work for the same reason just having another open tube past the MAF wouldnt work. You are getting a LOT of unmetered air into the system. Think of it like this. You are doubling the cross section of the entrance, which will not only let twice as much air through at the same velocity, it will slow the velocity of the air for a given rpm. Your ECU would not be able to compensate. Remember, you also only have ONE throttle body, which will be a restriction, plus whatever the limit of your turbos airflow is. A stock MAF can flow pretty good air and make good power, and if that isnt enough you can go to an oversize one. To give you an example, there are N/A mustangs out there feeding eight cylinders through one 70mm throttle body and putting out good numbers.

You could use dual ECUs with a true dual MAF setup, but why bother unless you are pushing to the ragged edge? I would say spend the time and money in other areas. Just my opinion.

greenstreak

· #3 · Nov 12, 2005

IMO it could be made to work but would be a tuning nightmare. Knowing exactly how much air is being bypassed would be an issue. The ecu also bases its fueling on knowing exacty how much airflow you are seeing. If you could adjust for airflow like on DSMLink I think it could be made to work but not on a stock ecu with a Safc.

0lmytsi

· #4 · Nov 12, 2005

I know the skylines have this and even retain it after going single so they have a single intake pipe that branches off to 2 mas/filters. But i suspect the ecu is calibrated for it, but you could try finding out more from those people. Not sure if the 300zx tt's run dual mafs, i know the 3000gt and the supra dont.
I think this setup would only be worth it if you are making Lots (600+) horsepower but you usually use a standalone at that level so...

V8killerTSi

· #5 · Nov 12, 2005

and you'd be having same problem as everyone with piggybacks and big injectors...low airflow, the ecu will go to lo load maps...specially timing map.

livnthedream

· #6 · Nov 12, 2005

the 300zxtt runs one maf. and i agree, i'd do mods elsewhere. dont try to reinvent the wheel.

LaserCool

· #7 · Nov 12, 2005

NEAWD said:
I was contemplating a dual maf setup on my DSM, which will give me twice the airflow and allow the stock ecu to control 900cc injectors with only mild tuning with an afc. I would allow one maf to be read by the ecu and have the other maf as a dummy. Now the ecu would have 1/2 the resolution as normal, but being as though the stock ecu map is rather extensive, it will only affect tunning a little.

A simpler idea would be to look around to see if there's a larger MAF availible. Since the cross -sectional area of the flow tube is just pi*r^2, then to double the volume of air in the system, one need only find a tube with a radius (sqrt2) times as big, or an extra 41%.

So, for example, the cross sectional area of a tube 3 inches in diameter (1.5 inches in radius) is 1.5^2*pi or 2.25*pi. Picking a pipe that is 1.5(1.41)*2 = 4.25 inches in diameter instead of 3 inches doubles the cross sectional area of the tube, and, all things being equal, doubles the volume of air reaching the motor at the same air flow speed.

Of course, all things are not necissarily equal, since Bernoulli's principle takes over, but it seems to me much more reasonable to see if there is already a MAF made which is bigger and one could spoof the ECU to take accurate readings from a fully functional MAF.

NEAWD

Discussion Starter · #8 · Nov 12, 2005

roughneck9725 said:
wouldnt work for the same reason just having another open tube past the MAF wouldnt work. You are getting a LOT of unmetered air into the system. Think of it like this. You are doubling the cross section of the entrance, which will not only let twice as much air through at the same velocity, it will slow the velocity of the air for a given rpm. Your ECU would not be able to compensate. Remember, you also only have ONE throttle body, which will be a restriction, plus whatever the limit of your turbos airflow is. A stock MAF can flow pretty good air and make good power, and if that isnt enough you can go to an oversize one. To give you an example, there are N/A mustangs out there feeding eight cylinders through one 70mm throttle body and putting out good numbers.

You could use dual ECUs with a true dual MAF setup, but why bother unless you are pushing to the ragged edge? I would say spend the time and money in other areas. Just my opinion.

This seem like kinda of a closed minded approach. You are using two mafs- one that is used by the ecu one that is a dummy to regulate how much air is coming in. Now even though the 2nd maf is not being monitored doesn't mean this is unmettered air; the air comming through the dummy mas is the same amount as through the monitored maf- therefore giving you 2x the airflow. Now with twice the airflow you can use twice the stock injector size and still have the stock ecu maintain a fairly good tune. Now the tuning does become more difficult with larger injectors, but I think a dual maf setup would be a great choice if you are trying to make a lot of power on a stock ecu.

eviltalon91

· #9 · Nov 12, 2005

can a maf-t system be converted to use a 4 or 4.5 inch aftermarket camaro mas by granatelli motorsports??? if so, i believe they have them in 100mm and 105mm( the 105mm is 4.13 inches in diameter close to the projected 4.25) if so, this could be made to work right??

roughneck9725

· #10 · Nov 12, 2005

ok, lets make this simple. why not just use two pipes then, one metered and one not, no MAF? Why the dummy maf? Same reason, unmetered air. Trying to explain this to you but your not getting it. Dummy MAF makes ZERO sense. it is unmetered air, same as an intake leak only bigger. Hell, why not just tune the engine to the intake leak? Tell you what, try it and see. It will not work well. Been working on cars for 14 years, some of that time for a living and been a racing freak longer than that. Been into fuel injection since the chevy TPI came out. Im not dissing you here, just trying to help you. Put your money and time somewhere else, or go in circles, your choice. Oh, and you still wont have twice the airflow, as you are still going through the ONE throttle body.

Since I am being negative here, let me try to give you a different approach. Put the time and effort into the cylinder head. Try pocket porting them. Or, put some money in a larger throttle body and single MAF. Maybe a better intake. Something that is PROVEN to make power. Good luck to you.

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NEAWD

Discussion Starter · #11 · Nov 12, 2005

roughneck9725 said:
ok, lets make this simple. why not just use two pipes then, one metered and one not, no MAF? Why the dummy maf? Same reason, unmetered air. Trying to explain this to you but your not getting it. Dummy MAF makes ZERO sense. it is unmetered air, same as an intake leak only bigger. Hell, why not just tune the engine to the intake leak? Tell you what, try it and see. It will not work well. Been working on cars for 14 years, some of that time for a living and been a racing freak longer than that. Been into fuel injection since the chevy TPI came out. Im not dissing you here, just trying to help you. Put your money and time somewhere else, or go in circles, your choice. Oh, and you still wont have twice the airflow, as you are still going through the ONE throttle body.

Since I am being negative here, let me try to give you a different approach. Put the time and effort into the cylinder head. Try pocket porting them. Or, put some money in a larger throttle body and single MAF. Maybe a better intake. Something that is PROVEN to make power. Good luck to you.

The dummy maf is to regulate the amount of airflow. This way it allows you to know how much air is comming in. With an open pipe it is hard to know how much air is comming in- this is how a dual maf setup would remain tunable- it lets you know how much air you are working with. It's easier than calculating the exact size tube you will need to flow as much as a maf, and it's exactly like having a really big maf.

Now 2g maf begins to overrun at a certain point. We'll say 450hp now if you want to maintain the stock ecu and want more than 450hp have 2 mafs- it allows you to have 2x the airflow before the maf overruns- allowing you to make more power.

Also I don't care how long you have been working on cars. And, did you say pocket porting? You need to go back to your cast iron head V8's. The stock 1g head flows more than the SB2 heads on Nascar engines.

Don't try to make me look stupid by showing how much experience you have. We all know how many half ass mechanics are out their that have been doing it for years. How am I supposed to know if you are one of those mechanics I don't.

So I will await your ego driven reply. And try to be more articulate when you speak to me.

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roughneck9725

· #12 · Nov 12, 2005

ok guy, do what you like. I just tried to help you. Good luck. Bye the way, I was a Mercedes Benz mechanic (Mercedes use a MAF) working for a dealership in Indy, not a backyard hack. They dont let retards touch a $135,000 car. Do what makes you feel good, hope it works for you.

NEAWD

Discussion Starter · #13 · Nov 12, 2005

roughneck9725 said:
ok guy, do what you like. I just tried to help you. Good luck. Bye the way, I was a Mercedes Benz mechanic (Mercedes use a MAF) working for a dealership in Indy, not a backyard hack. They dont let retards touch a $135,000 car. Do what makes you feel good, hope it works for you.

Works for me. On with the descussion then.

Steve93Talon

· #14 · Nov 14, 2005

Just buy a VPC

16g-95GSX

· #15 · Nov 14, 2005

This is what the Blue wire on the Safc is intended for, dual MAF's for cars like the 300zx. I posted about this years ago, I believe even in this same section of the board. That was the same thread that Mike originally began talking about his "new idea", the GM MAFT.

BoostaholicLS1

· #16 · Nov 15, 2005

I would suggest converting to speed density with a box like AEM

Matt_98GSX

· #17 · Nov 16, 2005

It seems to me like it could work, but would by no means be a precise way of tuning. If you used a dummy MAF with the same filter on it as the working MAF, they should in theory let in equal amounts of air (depending on how you did the rest of the piping). If they were both letting in the same amount of air, you could cut the signal to the ecu in 1/2, run double the size of the stock injectors and be somewhere in the ballpark. I wouldn't do it on my car, but I could see it working on someone else's

. The main problem would be ensuring that those 2 MAFs always flow the same amount of air.... You'd better hope that the working MAF filter doesn't get clogged or obstructed...

Liger

· #18 · Nov 16, 2005

This dual maf idea to me sounds rather pointless imho. you cannot meter the air or accurately guess how much air is being sucked in through the other intake tube without using some very complex algorithms and coding. It can be done but it would be such a huge amount of work for something that would not give you anymore power. You have one throttle body or method of air going into the intake manifold. So in turn you will have no more air entering the engine as did before. You may make it easier for the engine to breath but it would not even be noticeble. And our engines do not use enough air to warrant such a system. If you are wanting more air to enter the engine i would focus more on the bottlenecks like the throttle body, intake ports, exhaust ports, small piping...

Liger

· #19 · Nov 16, 2005 (Edited)

And also, you would have to have some sort of secondary or piggyback system to fake the ecu into thinking you are sucking in twice the amount of air into the engine. And along the lines of it sucking the same as the second intake, you would have to place the two units in a place where consistant air density between both air intakes could be accomplished and you would have to have equal lenth piping and same bends in order for it to work. In other words, you cannot have one intake sucking in lots of cold air from behind the headlight while the second one may be sucking in more hot air from the engine bay. The air will travel in the path of least resistance and colder air is more dense, thus offering more power but will throw off the readings if hot air is being sucked in on the other intake which will screw up your fuel trims. If some of you notice, you may hit fuel cut on a cold day but not a warm day, this is because when the air is hot it is not at dense. So you suck in 10 in^3 of air, now take 10 in^3 of hot air and put it at a fixed temp of 75 degrees, it will contract to less than 10 in^3 in volume while heat up the 10 in^3 of cold air to 75 degrees and it will expand to greater than 10 in^3 of air. So as you have a cold air flow and a hot airflow mixing to make a warm airflow going into your engine, you will have metered either one or the other flow, so you'll either be running too rich or too lean..

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thegreatms

· #20 · Nov 16, 2005

V8killerTSi said:
and you'd be having same problem as everyone with piggybacks and big injectors...low airflow, the ecu will go to lo load maps...specially timing map.

exactly. This is why you can only use a safc up to like 760 ingectors. Now you are forcing it to 900 injectors and don;t even have the control a SAFC will give you.

With injectors that big you HAVE to control timing.

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